Metalink

Metalink is a file format and protocol designed to facilitate the distribution and downloading of software files, particularly large ones. It aims to provide a more robust and efficient way to download compared to simple HTTP links. Metalink files, typically with a .meta4 extension, contain a wealth of information about the file being distributed. This includes multiple URLs from different servers or mirrors, checksums (like MD5, SHA-1, or SHA-256) to verify file integrity, and sometimes information about the file's size, language, and operating system compatibility.

The primary benefit of Metalink is its ability to offer redundancy and speed. Download managers that support Metalink can automatically select the fastest or most reliable server from the provided list. If one server fails or becomes slow, the download manager can seamlessly switch to another. The checksums embedded in the Metalink file are crucial for ensuring that the downloaded file has not been corrupted during transmission or tampered with. This integrity check is performed automatically by compliant download clients.

Metalink is an open standard, and its specification is maintained by the Metalink Project. It is designed to be extensible, allowing for future enhancements and features. While not as universally adopted as simple HTTP downloads, Metalink is employed by various software projects and content delivery networks to improve the user experience and reliability of software distribution. Its complexity compared to a direct download link means it requires specialized software to fully leverage its capabilities.